Conventional monohull yachts use a fixed keel and a separate mast and sail plan supported by a number of stays. As the mast is basically fixed in a generally vertical orientation, when a conventional yacht is sailed into the wind, the boat tends to tilt (or heel) to angles of around 15.degree. from the horizontal (ie. due to the action of the wind on the sails of the yacht).
It is known that yachts sail fastest when the hull is maintained approximately in a horizontal orientation, and various attempts have been made in the art to reduce the tilting (or "heeling") of yachts. For example, sail shapes have been changed to quickly release wind from the sail to minimise heeling. Current yacht designs attempt to change the shape of the main sail by displacing the mast towards the bottom of the boat whilst at the same time bending upwardly the bow and stern of the yacht. Considerable force is required to effect such alteration and a large amount of stress is induced in the sail craft to achieve such configurations.